SIM800L: Add FM radio support

[nagyrobi]

Describe the problem you have/What new integration you would like SIM800L: has a nice FM radio built-in. Has speaker output. Something like below would be nice:

• switch to turn radio ON/OFF (AT+FMOPEN and AT+FMCLOSE)
• number to set audio volume (AT+FMVOLUME)
• number to set FM frequency (AT+FMFREQ)
• action to start FM scanning (AT+FMSCAN)
• sensors with currently tuned in frequency and signal strength (AT+FMSIGNAL)

Implement it as media_player.

Please describe your use case for this integration and alternatives you've tried: The module could be very useful during idle times when no GSM usage is active.

Additional context https://cassiopeia.hk/arduinoradio/ https://cdn-shop.adafruit.com/datasheets/sim800_series_fm_application_note_v1.00.pdf

[nagyrobi]

This, combined with support for I2S audio input would make possible creation of FM-to-WebRadio receivers, which stream could be played in the network using other media players in any room.

[CCChelios]

This, combined with support for I2S audio input would make possible creation of FM-to-WebRadio receivers, which stream could be played in the network using other media players in any room.

I don't see the point in this. devices have access to the Internet and can play any audio stream.

[nagyrobi]

Point is, you don't wanna rely on the internet to listen to radio. Local streams only!

Also, there are radio stations broadcasting in FM but have no corresponding web stream.